Aerovee Oil System

[adoepner]

Hi everybody,

I recently purchased a Waiex equipped with the older AeroVee 2002. It has dual ignition, so is pretty much the same as the 2.1 except for the 20A alternator and a different crank.

The engine had only run for a few hours (and two flights) with the previous owner. During my inspection I noted excessive end play of the crank and a significant oil leak from the crankcase parting line. This cast doubt on the quality of the initial build, so I decided to have the engine rebuilt by an engine builder / machinist in the Minneapolis area.

After some lengthy discussions with the engine builder (who himself flies behind a VW in a 601), and a fellow Sonex owner who switched from an AeroVee to a Jab 3300, I decided that this was a good time to make some changes to the engine to hopefully make it lighter, a little more powerful, and more reliable - this will hopefully make me happier with it over the long term, in exchange for parting with a lot of money. ;)

Here is what I am having done:
- New crankshaft with 84mm stroke, chevy journals (to avoid case machining)
- New connecting rods
- New 94mm pistons
- New 94mm Nikasil cylinders
- Great plains prop hub and #1 bearing
- Compression ratio set to 8:1

The engine will be 2332cc when complete and should put out around 90 HP ... I shouldn't call it an AeroVee anymore. Timing is fixed with the AeroVee accessory case and will therefore remain at 28 deg before TDC. I will run it on AVGAS initially and plan to introduce MOGAS slowly, watching for detonation.

I will be adding a full flow oil filter to my engine, and this has caused me to spend some time thinking about the oil system. The AeroVee uses a dual relief case. With the oil cooler in the "stock" Sonex/Waiex location (below the sump), it seems like the full flow of oil is directed through the oil cooler at all times. This is less than ideal, since it will take the engine longer to warm up - though, the oil cooler is not getting much airflow while on the ground anyway. More important, however, is that the first oil pressure relief (at the hub end of the case), which bypasses the oil cooler when oil pressure across the top-mounted cooler is high (cold, thick oil), no longer has an oil temperature regulating function. Using a top mounted cooler would restore this function. I plan to fly in the Canadian winter, so this thermostatic function is important to me.

The other thing that I like about the top-mounted oil cooler is that it keeps the underside of the engine clear, making for easy oil changes. With a top-mounted oil cooler, I would close the lower inlet in the cowl as I think directing air over the sump would impede engine cooling - not improve it. Directing ram air into the lower part of the cowling reduces the pressure difference across the cylinders, heads, and top-mounted cooler. I'd be curious to see what the factory has to say, but I'm sure there is a reason that the Onex does not have this inlet. When running without an oil cooler, I can appreciate that airflow over the sump fins is important.

The potential for simplifying an eventual turbo installation makes me a big fan of the top-mounted oil cooler. Though, the turbo and my soon-to-be larger displacement may cause some cooling issues ... Finally, using a top-mounted cooler admits that the VW engineers knew what they were doing.

Unfortunately, my engine is in Minneapolis at the moment, and I am on the west coast. I am looking for some help finding some info:

1) I would like to know what size the "stock" oil pump is that ships from Sonex. I think this is just a measure of the diameter of a gear in the pump (21mm or 26mm or 30mm, etc.) - someone please correct me if I am mistaken.

2) I would appreciate it if someone would post some photos of the oil cooler bypass plate that bolts to the top of the case. I would like to see what it looks like from the underside to build an understanding of how oil flows through it (or is blocked by it).

3) I have seen oil filter mounts and oil pump covers with integrated pressure relief. Is there any merit to these? I'd like to avoid blowing a cooler or a filter and leaving a puddle on a taxiway after a run-up on a winter's day.

4) To those that have switched to a top-mounted oil cooler in a Sonex or Waiex - did you encounter any interference issues with the cowling?

5) I would like to hear about experiences with adjustable oil pressure relief valves. Where are these installed, at the oil pressure relief valve (oil cooler bypass - hub end) or at the oil pressure control valve (flywheel end)?

6) It seems to me that with the oil cooler bypass plate installed (for the "stock" Sonex/Waiex oil cooler installation), the oil pressure relief valve (oil cooler bypass - hub end) doesn't do much. Since this relief valve no longer bypasses the cooler, and the oil pressure control valve (flywheel end) is regulating oil pressure by directing flow to the sump, it looks to me like the system would function best if this relief was disabled. To disable it, it would need to be installed, but could be installed with a spring so stiff that it does not open. I'd appreciate it if an engine guru could chime in on this and correct me if I am mistaken.

This is a lot of info, with a lot of questions - Thanks in advance!

Andrew Doepner
Waiex W0014

[MichaelFarley56]

Hello Andrew,

First, congrats on the purchase of the new toy! The Waiex you purchased looks like a really nice airplane and I'm sure you'll have a lot of fun with it.

I'm in no way an expert, but I'll try to answer your questions as best as I'm able.

1. I believe Sonex uses the Maxi Pumps from www.cbperformance.com for the use on the AeroVee, such as part #1796 on that website. It looks like they are 26MM pumps but I could be mistaken. I think that's what the information states on CB's website.

2. I can try to take a picture of that the next time I make it to the airport but I don't have a picture of it right now. There may be a picture on the AeroVee online manual found here: http://www.aeroconversions.com/support/manuals.html As soon as I get back up to my hangar I'll try to get a picture of the plate.

3. Adding an oil filter to the system is a chance you'll have to decide on. Personally, I've heard way too many stories of people blowing oil filter seals on startup, so I'd much rather just change the oil more often and call it a day. Changing the oil every 25 hours, I feel, is more than sufficient. I just don't think a filter is worth the chance.

4. I have the top mounted oil cooler system on my Waiex and am happy with the change. Oil temps run a little warmer but not enough to worry about. I've flown on days where the outside air temp is in the low 80's, and my oil still doesn't get up to 200 degrees so I'm happy with it. As for interference...the factory told me that it's a tight fit and they're right. I had to file off a small flange off the oil cooler itself, then I had to add a small "dent" into my cooler top cover plate to make room for the cowling hinge. You may need to do that or remove a lug off the hinge itself to get adequate clearance.

5. I have the adjustable pressure relief valve on my engine. Install it on the rear oil plug nearest the flywheel. You can use this to make small adjustments on oil pressure. My own experience is that the valve will raise the pressure on startup, but only does a little once the oil is warm. That being said, be careful when making adjustments when the oil is cold; you don't want to blow a cooler.

6. The front oil bypass plug has an important function...venting overpressure situations. It's designed to be the first thing after the pump and will vent excess oil pressure back into the sump in the event of a cold oil start. Personally, I wouldn't mess change anything since you want that safety feature built in.

Hopefully this helps a little. Let me know if I can help with anything!

Mike

[falvarez]

I still have my Maxi Pump in the packaging that came with my AeroVee (which was originally intended for a ONEX with a top mounted oil cooler)....it shows that its from CB Performance with part #1795. I'm not sure if there are any differences between 1795 and 1796 so you may want to give them a call to figure out which one is best for your application.

Top Mounted Oil Cooler Maxi Pump

Oil Pump (640x427).jpg (148.04 KiB) Viewed 9425 times

[MichaelFarley56]

Thanks for the picture Frank! The information on the website says that there's a few different pumps of the same design depending on which case you have. I'm sure the part that Sonex sent you #1795 is the one Sonex sends out and is correct for the AeroVee. I'm glad you had the picture!

[adoepner]

Thanks for the info Mike and Frank. Sounds like a really tight fit for the top-mount. I hope the 26mm pump would not be able to generate sufficient pressure to blow an oil filter. In case that I discover it can, I am having the plug to the main oil galley of my case drilled and tapped for a pipe plug. This will allow me to return oil there, instead of at the pump, and change my pump cover to one with a built-in pressure relief (example http://www.geneberg.com/product_info.ph ... cts_id=320).

There are a few pictures of the oil filter bypass plate in the manual, but they are all from above (when it is mounted on the case). I would like to see it from below - to see the oil passages and o-rings/seals.

Mike - could you please take a photo of your oil cooler filing and dent?

Thanks,

Andrew

[rizzz]

In case that I discover it can, I am having the plug to the main oil galley of my case drilled and tapped for a pipe plug. This will allow me to return oil there, instead of at the pump, and change my pump cover to one with a built-in pressure relief (example http://www.geneberg.com/product_info.ph ... cts_id=320).

That's what I have on mine:
http://www.vwaircraftengines.com/viewto ... ?f=20&t=58
haven't chosen a suitable oil cooler/filter yet though.

[radfordc]

1) I would like to know what size the "stock" oil pump is that ships from Sonex. I think this is just a measure of the diameter of a gear in the pump (21mm or 26mm or 30mm, etc.) - someone please correct me if I am mistaken.

The numbers refer to the thickness of the gear...not the diameter. Aerovee uses a 26mm pump.

[mike.smith]

In case that I discover it can, I am having the plug to the main oil galley of my case drilled and tapped for a pipe plug. This will allow me to return oil there, instead of at the pump, and change my pump cover to one with a built-in pressure relief (example http://www.geneberg.com/product_info.ph ... cts_id=320).

That's what I have on mine:
http://www.vwaircraftengines.com/viewto ... ?f=20&t=58
haven't chosen a suitable oil cooler/filter yet though.

Where are the pushrod tubes? I saw the pushrods in the photos, but no tubes running from the engine to the head.

Mike Smith

[rizzz]

In case that I discover it can, I am having the plug to the main oil galley of my case drilled and tapped for a pipe plug. This will allow me to return oil there, instead of at the pump, and change my pump cover to one with a built-in pressure relief (example http://www.geneberg.com/product_info.ph ... cts_id=320).

That's what I have on mine:
http://www.vwaircraftengines.com/viewto ... ?f=20&t=58
haven't chosen a suitable oil cooler/filter yet though.

Where are the pushrod tubes? I saw the pushrods in the photos, but no tubes running from the engine to the head.

Mike Smith

Those were not installed at that point, those pictures were taken when the engine was still at the previous owner, he was working on the valve train geometry etc at the time.
I have a set of new Scatt pushrods & solid rocker shaft upgrade that will still need to go in before finalizing all that.

You can see the tubes in this picture temporarily installed when the engine was about to be shipped to me:

crate 2.JPG (353.53 KiB) Viewed 9357 times

[adoepner]

radfordc - thanks. Thickness makes more sense.

Could anyone please let me know what heads come stock with the Aerovee?

Andrew